1. Field of the Invention
This invention relates to the lost-wax casting process, more specifically, it relates to an inexpensive vacuum casting chamber to increase production in vacuum assist casting machines. The function of the present invention, may be adapted and employed for a variety of requirements as those skilled in the art will recognize, in the light of the present disclosure.
2. Description of the Prior Art
Since 1969, casting machine manufacturers have marketed several versions of vacuum casting machines, the most popular version being the vacuum assist casting machine. the body of the machine contains a vacuum pump. Allocated at the front of the machine is a switch to actuate the vacuum pump, a vacuum release valve, and a vacuum gauge. The top of the machine serves two purposes, on one side the investment material can be vacuumed, and on the other side a non-perforated flask can be used in casting. After the wax patterns have been enclosed in a flask, a heat resistant plaster compound called an investment, is mixed with water in a rubber bowl, and then placed on top of the machine and under a bell jar to be vacuumed, to eliminate the air trapped in the investment. The investment slurry is then poured into the flask to form the final mold for the metal.
The flask after it has been burned out and has reached the proper casting temperature is placed on the other side of the machine, sprue opening side up and directly over the vacuum hole in the plate (called vacuum table) which is connected to the vacuum pump. A switch is used to actuate the pump, which evacuates air from the flask and draws the molten metal into the flask.
The vacuum assist casting machine is very easy and safe to operate, and is widely used by craftsmen and small casting outfits. But the vacuum assist casting machine has a shortcoming, production is very restricted to only a few wax patterns per flask, because the vacuum is created at the bottom of the flask, only a non-perforated flask can be used with this type of machine, and a tall flask is not recomended for small pieces of jewelry.
In vacuum assist casting machine, the vacuum force acts only in one direction, from the top of the flask downward, and when making the wax tree, the wax patterns have to be attached to the sprue base facing downward, at a very acute angle with respect to the sprue base. By doing this type of treeing, less wax patterns can be attached to the sprue base, this is necessary otherwise castings with voids or incomplete casting will be the result.
There is no alternative for owners of vacuum assist casting machine to increase production with out the need of acquiring a more expensive vacuum chamber casting machine, which utilizes perforated flask.